Hearts!

Stars and horseshoes to come . . .

Cardiac Output: the minute volume of the heart Stroke volume x heart rate Normal resting left ventricular stroke volume= 70 mL Normal resting heart rate 70 bpm Normal left ventricular cardiac output= 4900 mL

Things you can mess with Squeeziness (inotropy), relaxiness (loositropy),

speediness (chronotropy), and electricaliness (dromotropy).

The measurable components of the heart The mechanical beating of the heart (measured by

peripheral pulses) The electrical conduction of the heart (measured by

EKG) And the perfusion of the heart muscle (measured by

diastolic pressure)

Depolarization: your electrical system

Syncitia! They makes depolarization weird

Blockers! You can mess with depolarization Four classes of antiarrhythmics: Class I: Sodium channel blockers (Lidocaine) Class II: Beta Blockers (Propanolol) Class III: Potassium channel blockers (Amiodarone) Class IV: Calcium channel blockers (Diltiazem)

Pressors The opposite of beta blockers Used for low blood pressure in the absence of

hypovolemia Dopamine commonly used in EMS Dopamine’s effects are indirect, though Epinephrine can be used. Much more direct Norepinephrine can be administered by a physician

EKGs Are a lot more complicated than everyone makes them

out to be. But you don’t have to understand how they work to use

them. You only have to resort to the metrics that define a

rhythm when it’s not obvious. Obviousness comes with seeing lots of rhythms.

EKG

Hearts, as seen by Warren Budd Electrolyte dysrhythmias Infectious Etiologies Decreased perfusion Aneurysm Conduction abnormalities Myocardial weakness Pericardial effusion/tamponade

Your heart uses blood And if that blood’s electrolytes are wonky, that can cause

depolarization changes Some are easy to see on an EKG and hard to determine

clinically Hyper/hypo -calcemia, -magnesemia, -kalemia, -natremia

Heart muscle can get tired, too The way your skeletal muscles get tired is by decreased

ability to oxygenate the muscle and offload CO2 Your heart muscle doesn’t overwork, it just under-

perfuses. Hypoperfusion is caused by blockages in the arteries that

feed the muscle. That muscle will accumulate lactic acid as it works

anaerobically, causing angina pectoris Eventually that muscle will die (or infarct), leading to a

myocardial infarction, or ‘heart attack.’ Once 70% of this ventricular muscle is dead, heart failure

is imminent.

Aneurysm (dissection) Just a defect in the wall of a vessel The medical relevance of this is either dissection or

rupture A dissection of an aneurysm is when the inner layer of

the blood vessel (tunica intima) peals away from the rest of the vessel (usually at the tunica media, the muscular layer)

This flap of tunica intima can force blood into the space between the tunica intima and the tunica media, creating a “false lumen.”

This false lumen can grow big enough to occlude the real lumen, causing decreased or absent perfusion to vessels.

Aneurysm (rupture) A ruptured aneurysm is much more obviously

catastrophic. The vessel bursts, pouring blood into the interstitium. While this can bleed can eventually tamponade itself with

hydrostatic pressure, it normally does so to the detriment of the tissues around it.

In the brain, this means death In the abdomen, the cavity too big to fill, so the

hydrostatic pressure of the peritoneum never gets high enough to tamponade the artery and results in bleeding to death (exsanguination).

Conduction abnormalities Electrical impulses and change in the polarity of

myocardial cells are what causes the heart muscle to contract.

There’s a set route on which these impulses travel. Impulses can go the wrong way sometimes, which is less

efficient, leading to the heart beating inefficiently. There are places that this goes wrong much more

frequently than others, like the Bundle of Kent. The result is an abnormal rhythm, which may not perfuse

the brain.

Myocardial weakness You heart muscle has an optimum range in which it

contracts most forcefully If your blood pressure is too high, it will stretch heart

muscle past that range This will weaken the heart muscle, causing it to beat

irregularly, or to dilate This eventually leads to blood “backing up the system.” It most frequently back up into the lungs, causing

pulmonary edema, And the feet, causing pedal edema It does it other areas in the body as well, but the feet

have gravity and distance working against it.

Pericardial Tamponade If the sack that holds your beating heart fills with blood

or pus, (pericardial effusion) then your heart will not be able to relax to its full size and fill the ventricles all the way.

This decreases the amount of blood you can pump. The only definitive treatment for this is to drain

pericardial sac Which can be done by a needle (pericardiocentesis) Or by cracking the chest open, grabbing the heart,

knicking a hole in the sack, and squeezing (expressing) the fluid (open thoracotomy)

Your heart can be infected Just like every other tissue in the body Pericarditis Myocarditis Endocarditis

Pericarditis ST elevation in literally every lead.

Myocarditis

Endocarditis Vegetation can grow on valves, acutely causing a new

heart murmur Occurs in IV drug users

Murmurs: an art in appreciation Murmurs are funny sounds your heart makes when blood

rushes through various apertures when it shouldn’t There are systolic murmurs and diastolic murmurs Systolic murmurs are caused my stenosed valves Diastolic murmurs are caused by prolapsed valves They can occur at any of the four valves (bicuspid,

tricuspid, pulmonary, and aortic) There are also murmurs caused by malformations in the

heart (atrioseptal defects, vetriculoseptal defects)

Tachycardia Algorithm

Bradycardia Algorithm